Cotnpejisafory Motions 457 



(I On turntable responds as normal, but more slowly. 



e Responds as normal to "revolving environment." 



3 After one week: 



a Lies on back indefinitely, quietly. 



b Rights itself more easily than before, but still awkwardly. 



c Walks about unsteadily; leaps awkwardly, falling on side. 



(J On turntable, responds normally. 



Another frog, with both sets of semicircular canals destroyed 

 by boring into capsule from the dorsal side, showed after three 

 weeks a marked lack of coordination of movements, though not as 

 great as at first; this was evident in swimming as well as in walk- 

 ing, and in both swimming and in jumping the animal frequently 

 turned over on its back; it righted itself rather quickly, but move- 

 ments still showed awkwardness. On turntable, responses were 

 as in the normal animal. 



As has been pomted out above, the summation of mechanical 

 disturbances or accelerations on the rotation of an animal upon 

 the turntable in a given direction seems to depend upon the posi- 

 tion of the animal with reference to the axis of rotation, whereas 

 the sense of the response in relation to the animal's own axis is 

 constant. Thus, the rotation being to the right (clockwise), the 

 factor of wind, or resistance of the air, acts upon the right side 

 of the animal if the animal faces the periphery, but on the left side 

 of body if the animal faces the pivot; but in any case the response 

 is to the left. The same apparent contradiction is observed if we 

 consider the direction of the centrifugal force of the rotation; the 

 direction of the centrifugal pressure ot the viscera or other loose 

 parts, of the strains on the skeletal articulations, and of the 

 friction of the body on the supporting surface, is toward the 

 periphery, however the animal maybe placed; but the response to 

 a given rotation is constant with reference to the axis of the animal. 

 The same apparent contradiction is found when the attention is 

 directed to the inertia of the viscera or of the contents of the semi- 

 circular canals. In addition to these contradictions is the fur- 

 ther fact pointed out by Schafer in 1887 and by others, and re- 

 ferred to above (§4), that the inertia of the head, because of its 

 loose articulation to the trunk, is sufficient to account for the 



